Investigation of drying characteristics of some heat-sensitive materials in a multi-mode heat pump drying system

Abstract

<P>THE AIM OF THIS PROJECT IS TO DEVELOP A HEAT PUMP-ASSISTED DRYING SYSTEM FOR EFFICIENT DRYING OF HEAT-SENSITIVE MATERIALS. A TWO-DIMENSIONAL DRYING MODEL WAS DEVELOPED ASSUMING THE DRYING RATE TO BE CONTROLLED BY LIQUID WATER DIFFUSION. EXPERIMENTAL STUDIES WERE CONDUCTED USING A BATCH HEAT PUMP DRYER DESIGNED TO PERMIT SIMULTANEOUS APPLICATION OF CONVECTIVE, RADIANT AND CONDUCTIVE HEAT. POTATO WAS USED AS A TYPICAL HEAT-SENSITIVE MATERIAL SINCE ITS HYGRO-THERMAL PROPERTIES HAVE BEEN WELL CORRELATED BY SEVERAL EARLY WORKS. BOTH DRYING KINETICS AND TEMPERATURES WITHIN THE SLAB DURING DRYING SHOWED GOOD ACCORD WITH MEASUREMENTS. THIS TWO-DIMENSIONAL DRYING MODEL CAN ALSO BE USED TO ANALYZE A LARGE SCALE DRYING SYSTEM UTILIZING A MULTIPLICITY OF SINGLE SLAB-LIKE DRYING OBJECTS TO SIMULATE A PRACTICAL DRYER OPERATION. EXPERIMENTS USING MULTIPLE TRAYS WERE CARRIED OUT TO INVESTIGATE THE SPATIAL VARIATION OF DRYING RATES INSIDE THE DRYING CHAMBER. SWEET POTATO AND CARROT SLABS WERE USED I